Presence information comprises a dynamic profile of an entity (typically referred to as a “presentity”, “publisher” or “provider”), which is visible to others (sometime referred to as “subscribers”). This dynamic profile can be used for multiple purposes, such as to control a presentity's communication, to share relevant information with subscribers, and to control network-based services. In addition, applications and services (e.g., advertising, weather service) can also publish or use presence information.
Presence information makes communication more effective and appropriate, allowing a subscriber to see whether the other party (presentity) is available and what is the most suitable way to contact that person (e.g., place a call or send a message). Not only can individuals publish their presence information, but also companies and applications can use presence information for advertising and as an information channel. Presence is also a powerful tool that enables users to personalize how they appear in other devices through the presence-enhanced devices such as a mobile phone book. Services such as online games and instant messaging make use of presence information.
Presence information can be used in many ways. Individuals can publish their presence information and check the presence information of others. In essence, presence does two things, it makes one person's presence information available to others and it makes the presence information of others available to the one person. Because presence enables rich forms of expression, including images and text, it can be used to control personal appearance to those who are interested in the user. Presence enables users to control their communication more effectively, indicating when, how, and to whom users are available. Communication also can be stimulated with presence. This provides for appropriate communication for both the initiating and receiving party, whether the communication is voice calls, messaging, voicemail, etc. Presence information can be used for context sharing. The sharing of presence information gives people the possibility of indicating their status, and can identify anything from location, moods, and emotions, to context and preferred means of communication, or an alternative contact. Presence information can be anything that is relevant for subscribers to know and what the publisher is willing to share. The presence publisher can be any object, including a person, a parcel package being delivered, a vending machine out of stock, or a computer related system or device. Presence systems work reasonably well when dealing with people in the same time zone. They also work adequately when dealing with people located in known, different time zones. Conventional presence systems are described in Request For Comments (RFC)-2778, the disclosure of which is hereby incorporated by reference.